As described in, for example, JP-A-11-15392 and JP-A-11-291817, display devices in which a half mirror material is disposed on a front surface of an image display member, such as a liquid crystal display device, have been known as display devices capable of switching to a mirror status that reflects outside light (or a mirror disposed with a display function). In these display devices, because outside light reflected by the half mirror material becomes greater than image light transmitted through the half mirror material when a lighting system is turned off or when an image is a dark display, the state becomes a mirror status. Conversely, because the image light transmitted through the half mirror material becomes greater than the outside light reflected by the half mirror material when the lighting system is turned on or when an image is a bright display, the state becomes an image display status. That is, in these display devices, it is possible to change the same viewing screen between a mirror status and an image display status by switching the brightness of the image display member at the half mirror material rear surface.
Also, in the republished publication of International Publication No. WO99/04315, a liquid crystal display device capable of switching between an open shutter state, in which an image display is viewed, and a closed shutter state, in which the image display is not viewed, is disclosed. According to this publication, it is written that outside light is reflected and becomes “metallic” at the time of the closed shutter state.
The liquid crystal display device of the republished publication of WO99/04315 is one in which two liquid crystal display panels, in which a liquid crystal layer is injected into a gap between a pair of substrates disposed with electrodes, are stacked, and a polarizing plate is disposed at three places on an upper surface and a lower surface of the two stacked liquid crystal display panels, and between the two liquid crystal display panels. Of these polarizing plates, a reflective polarizing plate, which transmits a predetermined linear polarization and reflects a linear polarization whose polarization axis is orthogonal to that of the predetermined linear polarization, is used as the polarizing plate disposed between the liquid crystal display panels. The transmission polarization axis of the reflective polarizing plate is parallel to the transmission polarization axis of the polarizing plate on the upper surface of the two stacked liquid crystal display panels. Also, a Twist Nematic liquid crystal is used for the liquid crystal of the liquid crystal display panel of the upper side (viewer side). In this configuration, when a voltage applied to the liquid crystal layer of the liquid crystal display panel of the upper side is small, the light transmitted through the polarizing plate of the upper surface is strongly reflected due to reflectance characteristics of the reflective polarizing plate, because the polarization direction is rotated 90 degrees and the light reaches the reflective polarizing plate when it is transmitted through the liquid crystal layer. Thus, the state becomes the “metallic” closed shutter state. Conversely, when a voltage applied to the liquid crystal layer of the liquid crystal display panel of the upper side is large, the polarizing plate of the upper side, the liquid crystal display panel of the upper side, and the reflective polarizing plate becomes an effectively transparent state and the state thereof becomes the open shutter state in which the image display of the liquid crystal display panel of the lower side is viewed. That is, due to the voltage applied to the liquid crystal display panel of the upper side, it is possible to switch between the closed shutter state, in which outside light is reflected and “metallic” is provided, and the open shutter state, in which the display of the liquid crystal display panel of the lower side is viewed.